Most people think in nominal terms, so the chart below illustrates the current dollar values for the six cohorts across the 50+ year period (in other words, the value of a dollar at the time received — not adjusted for inflation). What we see are the nominal growth patterns over the complete data series. In addition to the five quintiles, the Census Bureau publishes the income for the top five percent of households.

All segments showed an increase in year-over-year in average household income - again in current dollars. As for the cumulative household income growth by segment over the past 50+ years, the adjacent table shows the real, inflation-adjusted, difference between 1967 and 2019.

Below is the same chart as above, just inflation-adjusted (2019 dollars).

To give us a better idea of the underlying trends in household incomes, we've also prepared a chart of the real percentage growth since 1967. Note in particular the growing spread between the top quintile (and especially the top 5%) and the other four quintiles. The growth spread began in the mid-1980s during the Reagan administration, the era of Supply Side Economics (aka "Reaganomics" and Trickle-Down Economics). As this chart illustrates, tax and other policy changes to benefit the wealthier households didn't have the heavily promoted trickle-down effect. We've also highlighted recessions to show the correlation of household incomes to the business cycle.

All cohorts saw decreases in 2020, with the bottom quintile seeing the least since 2018 with -5.7% from 2019. The table below documents the percent change from the peak year - 2019 is the highest on record for all cohorts.

It's important to understand that the data in the charts above is for the mean (average) income for each of these segments. For US households quintiles, the mean (average) income is higher than the median (middle of the range). We'll have more to say about this negative skew in a follow-up article on household incomes by age bracket.

Read more updates by Jill Mislinski